1. Field of the Invention
The invention relates to DVD-ROMs, and more particularly, to programming a device with a reduced number of pins in an embedded system.
2. Description of the Related Art
FIG. 1 shows a conventional embedded system 100 with an externally coupled program provider 110. The embedded system 100 may be part of a DVD-ROM storing copyright information, or part of a general purpose digital device executing various applications programmed therein. The embedded system 100 typically comprises a program controller 120 and a programmable device 130. The program controller 120 accesses the programmable device 130 via a plurality of pins 105. The definition of each pin 105 is dependent on the type of device 130. When the programmable device 130 needs to be programmed with a specific application, a program code #DATA corresponding to the application is provided externally through a program provider 110. Conventionally, additional control pins such as 107 and 109 are required to perform the programming, through which the program provider 110 directly connects to the programmable device 130. One or more multiplexers 103 may be implemented on each pin 105, selecting signals from the program provider 110 or program controller 120 as an input to the programmable device 130. When programming, the multiplexers 103 select signals delivered via the control pins 107 to program the programmable device 130, while some additional signals are directly sent via the control pins 109. In some cases, the program provider 110 directly connects the program controller 120 by a bus 101, and the program controller 120 may comprise a level shifter (not shown) to map signals delivered via the bus 101 to each pin 105. The control pins 107 and 109 are still indispensable in the conventional architecture. There may be various types of programmable device 130, each conforming to different pin standards, and the program provider 110 performs the programming by executing a command sequence #CMD specifically designed for the programmable device. The layout of the control pins 105, 107 and 109 are also type dependent, as well as the signal protocol used by the program provider 110 and program controller 120. This architecture is deemed inflexible because the program provider 110, program controller 120 and corresponding pins can not provide compatibility when the programmable device 130 needs upgrade. Thus, a flexible architecture is desirable.